The present invention relates to microscope objectives, and more particularly, to an achromatic microscope objective with a numerical aperture of substantially 0.25 having four components. It is an object of this invention to provide such a microscope objective which is well-corrected for the usual chromatic image aberrations as well as spherical aberration, coma and astigmatism, while providing a substantially flat image field of 24mm and a 10X magnification in combination with a telescope objective as described in U.S. Pat. No. 3,355,234 and a typical 10X eyepiece.
The closest known prior art is U.S. Pat. No. 3,041,934 issued July 3, 1962 to Rubin et al. This patent discloses a flat field objective having five elements. The principal distinguishing differences of the objective of the present invention and reference resides in the reversed position of the second and third elements; the absence of a doublet in the prior art objective and the prior art objective does not provide parallel light exiting the last member of the objective.